System Design Interview Questions
Practice 1,018 real System Design interview questions for 2026 — System Design interview questions drawn from actual interviews with detailed solutions to power focused interview preparation. Coverage spans big tech patterns and company-specific flavors from Meta, Amazon, OpenAI, DoorDash, and Google, emphasizing software-engineering fundamentals: high-level architecture, APIs, data models, scaling strategies, and component-level tradeoffs you’ll need to codify on a whiteboard or virtual diagram tool. What’s distinctive in 2026: interviewers evaluate your ability to reason about capacity, latency, consistency, fault tolerance, and operational ownership while making measurable tradeoffs; expect more questions about AI/LLM inference pipelines, vector search and feature stores alongside classic problems like caching, sharding, messaging, and geo-distribution. Prepare by practicing clear HLD-to-LLD transitions, writing concise API contracts, doing back-of-envelope capacity math, and running timed mock interviews that force diagram clarity and follow-up handling. Focus on metrics, failure modes, and deployment/monitoring choices — those separate good answers from great ones.
"I got asked a hardcore MCM DP question and I saw it on PracHub as well. Solved that question in 5 minutes. Without PracHub I doubt I could solve it in 5 hours. Though somehow didn't get hired, perhaps I guess I solved it too fast? /s"
"Believe me i'm a student here jn US. Recently interviewed for MSFT. They asked me exact question from PracHub. I saw it the night before and ignored it cause why waste time on random sites. I legit wanna go back and redo this whole thing if I had chance. Not saying will work for everyone but there is certainly some merit to that website. And i'm gonna use it in future prep from now on like lc tagged"
"10 years of experience but never worked at a top company. PracHub's senior-level questions helped me break into FAANG at 35. Age is just a number."
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"Got a Google recruiter call on Monday, interview on Friday. Crammed PracHub for 4 days. Passed every round. This platform is a miracle worker."
"I've used LC, Glassdoor, and random Discords. Nothing comes close to the accuracy here. The questions are actually current — that's what got me. Felt like I had a cheat sheet during the interview."
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"PracHub Premium for one month cost me the price of two coffees a week. It landed me a $280K+ starting offer."
"Literally just signed a $600k offer. I only had 2 weeks to prep, so I focused entirely on the company-tagged lists here. If you're targeting L5+, don't overthink it."
"Coaches and bootcamp prep courses cost around $200-300 but PracHub Premium is actually less than a Netflix subscription. And it landed me a $178K offer."
"I honestly don't know how you guys gather so many real interview questions. It's almost scary. I walked into my Amazon loop and recognized 3 out of 4 problems from your database."
"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."
"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Design a search-to-ads ranking pipeline
Prompt Design a high-level search + ads ranking system for an app where a user issues a query and the product shows a mix of organic search results an...
Design a simple greeting-card web app
Design a web application for creating and viewing text-only greeting cards with an emphasis on shipping quickly (MVP). Core user stories - A user can ...
Design short URL service with click counting
Design a production-ready service that: 1. Creates a short URL for a given long URL (URL shortening). 2. Redirects when a user visits the short URL. 3...
Design a Top-K trending items service
Design a system that returns the Top K items (e.g., videos/posts/products) by popularity. Requirements - API to fetch: GET /topk?window=10m&k=100 retu...
Design a team chat system
Design a team chat system similar to Slack. The system should support: - One-to-one direct messages - One-to-many or group conversations (channels or ...
Discuss productionizing event-timeout detector
System Design: Production-Ready Event-Timeout Detector You are designing a production service that detects when an event fails to occur within a speci...
Scale Digit-Square Convergence Requests
Design a service that receives very high request volume for the digit-square convergence operation. For each request, the input is a positive integer ...
Design a multimodal RAG assistant
Prompt Design a Retrieval-Augmented Generation (RAG) system that can answer user questions using an internal knowledge base containing multiple modali...
Design weekly comment digest
Design a service that sends a weekly email digest of the top comments on each post to the post owner. Requirements: - Posts receive comments throughou...
Build an API aggregator with concurrency and retries
Build an Aggregation Service with Parallel Calls, Timeouts, Retries, and Observability Context You are designing a backend service that exposes a sing...
Design a prioritized log manager with eviction
Design a Log Store with Priority- and Recency-Aware Eviction Context You are designing an in-memory (or on-disk) log storage component. Each inserted ...
Design an ads data model
System Design / Data Modeling: Ads Data Model Design the data model (logical schema) for an ads platform that supports: - Advertisers creating campaig...
Design real-time modules communication and overload handling
You are designing a real-time system running on a single machine with two modules (e.g., producer -> consumer) that must communicate with low latency....
Design scenario-based speaking feature
System Design: Scenario-Based Speaking Practice for a Multilingual Learning App Goal Design a scenario-based speaking practice feature where users sel...
Describe CAP, distributed systems, multithreading experience
CAP Theorem, Distributed Systems Design Decisions, and Multithreading Context Provide a structured answer that both explains the concepts and shows ho...
Design a price tracking platform
System Design: Price Tracking Platform for E-commerce Context Design a system that tracks prices across many e-commerce sites, builds historical price...
Design secure Kubernetes with CI/CD
Kubernetes Architecture, Troubleshooting, Security, and CI/CD (GKE/EKS) Context: You are the on-call software engineer for a managed Kubernetes cluste...
Design a scalable food news feed
System Design: News Feed for a Food Discovery App Context You are designing a news-feed feature for a mobile/web food discovery app where users explor...
Design real-time top-K products service
System Design: Real-Time Top‑K Purchased Items Over Rolling Windows Design a real-time service that ingests purchase events and continuously outputs t...
Design distributed transactions protocol
System Design: Distributed Transactions Across Multiple Services Context You must design a distributed transactions protocol to coordinate updates acr...